A055504 n*(n-1)*(n-2)*(n-3)*(n-4)*(2*n-1)/72.

0, 0, 0, 0, 0, 15, 110, 455, 1400, 3570, 7980, 16170, 30360, 53625, 90090, 145145, 225680, 340340, 499800, 717060, 1007760, 1390515, 1887270, 2523675, 3329480, 4338950, 5591300, 7131150, 9009000, 11281725, 14013090, 17274285, 21144480

Offset: 0

Author

N. J. A. Sloane, Jul 10 2000

Keywords

• nonn
• easy

References

• L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 73, Problem 3.

Links

• Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).

Formula

G.f.: 5*x^5*(3+x)/(1-x)^7. [Colin Barker, May 09 2012]